scholarly journals A gain-of-function mutation in the GRIK2 gene causes neurodevelopmental deficits

2017 ◽  
Vol 3 (1) ◽  
pp. e129 ◽  
Author(s):  
Yomayra F. Guzmán ◽  
Keri Ramsey ◽  
Jacob R. Stolz ◽  
David W. Craig ◽  
Mathew J. Huentelman ◽  
...  
Keyword(s):  
De Novo ◽  
Receptor Gene ◽  
Expression System ◽  
Functional Characterization ◽  
Cell Voltage ◽  
De Novo Mutations ◽  
Gain Of Function ◽  
Whole Exome ◽  
Neurodevelopmental Abnormalities

Objective:To identify inherited or de novo mutations associated with a suite of neurodevelopmental abnormalities in a 10-year-old patient displaying ataxia, motor and speech delay, and intellectual disability.Methods:We performed whole-exome sequencing of the proband and her parents. A pathogenic gene variant was identified as damaging based on sequence conservation, gene function, and association with disorders having similar phenotypic profiles. Functional characterization of the mutated protein was performed in vitro using a heterologous expression system.Results:A single de novo point mutation in the GRIK2 gene was identified as causative for the neurologic symptoms of the proband. The mutation is predicted to change a codon for alanine to that of a threonine at position 657 (A657T) in the GluK2 kainate receptor (KAR) subunit, a member of the ionotropic glutamate receptor gene family. Whole-cell voltage-clamp recordings revealed that KARs incorporating the GluK2(A657T) subunits show profoundly altered channel gating and are constitutively active in nominally glutamate-free extracellular media.Conclusions:In this study, we associate a de novo gain-of-function mutation in the GRIK2 gene with deficits in motor and higher order cognitive function. These results suggest that disruption of physiologic KAR function precludes appropriate development of the nervous system.

scholarly journals Movement disorder in GNAO1 encephalopathy associated with gain-of-function mutations

Neurology ◽  
2017 ◽  
Vol 89 (8) ◽  
pp. 762-770 ◽  
Author(s):  
Huijie Feng ◽  
Benita Sjögren ◽  
Behirda Karaj ◽  
Vincent Shaw ◽  
Aysegul Gezer ◽  
...  
Keyword(s):  
Movement Disorder ◽  
Movement Disorders ◽  
Adrenergic Receptor ◽  
Molecular Mechanisms ◽  
De Novo ◽  
Site Directed Mutagenesis ◽  
De Novo Mutations ◽  
Gain Of Function ◽  
Mammalian Expression

Objective:To define molecular mechanisms underlying the clinical spectrum of epilepsy and movement disorder in individuals with de novo mutations in the GNAO1 gene.Methods:We identified all GNAO1 mutations reported in individuals with epilepsy (early infantile epileptiform encephalopathy 17) or movement disorders through April 2016; 15 de novo mutant alleles from 25 individuals were introduced into the Gαo subunit by site-directed mutagenesis in a mammalian expression plasmid. We assessed protein expression and function in vitro in HEK-293T cells by Western blot and determined functional Gαo-dependent cyclic adenosine monophosphate (cAMP) inhibition with a coexpressed α2A adrenergic receptor.Results:Of the 15 clinical GNAO1 mutations studied, 9 show reduced expression and loss of function (LOF; <90% maximal inhibition). Six other mutations show variable levels of expression but exhibit normal or even gain-of-function (GOF) behavior, as demonstrated by significantly lower EC50 values for α2A adrenergic receptor–mediated inhibition of cAMP. The GNAO1 LOF mutations are associated with epileptic encephalopathy while GOF mutants (such as G42R, G203R, and E246K) or normally functioning mutants (R209) were found in patients with movement disorders with or without seizures.Conclusions:Both LOF and GOF mutations in Gαo (encoded by GNAO1) are associated with neurologic pathophysiology. There appears to be a strong predictive correlation between the in vitro biochemical phenotype and the clinical pattern of epilepsy vs movement disorder.

scholarly journals A39 NOVEL GAIN OF FUNCTION NON-RECEPTOR TYROSINE KINASE MUTATIONS ARE LINKED TO THE PATHOGENESIS OF VEOIBD

2020 ◽  
Vol 3 (Supplement_1) ◽  
pp. 46-48
Author(s):  
M Mehta ◽  
L Wang ◽  
C Guo ◽  
N Warner ◽  
Q Li ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Western Blot ◽  
Receptor Tyrosine Kinase ◽  
Blot Analysis ◽  
Western Blot Analysis ◽  
Intestinal Inflammation ◽  
De Novo ◽  
Single Gene ◽  
Gain Of Function

Abstract Background Very early-onset inflammatory bowel disease (VEOIBD) is an emerging global disease, that results in inflammation of the digestive tract. Severe forms of VEOIBD can be caused by mutations in a single gene (monogenic variants) and, can result in death. A candidate gene which codes for a non-receptor tyrosine kinase (nRTK) has recently been implicated as a monogenic cause of IBD (unpublished). Whole exome sequencing was performed in two unrelated children who presented with symptoms of IBD identifying two distinct de novo gain of function mutations (S550Y and P342T). Both mutations are located in the highly conserved region of the nRTK, and were predicted to have similar downstream effects. Furthermore, four other patients with a variety of adult-onset immune disorders have recently been identified with rare variants in the same gene (M450I, R42P, A353T, V433M, S550F) but, their potential gain of function status remains to be determined. Studies show that this nRTK is an essential mediator in inflammation. It is expressed in both intestinal epithelial and immune cells however, its role in infantile IBD is unclear. This protein is first activated by phosphorylation and is linked to activating downstream transcription factors such as ERK and JNK. All these target proteins play a meaningful role in intestinal inflammation in patients with IBD. Aims Since we identified P342T and S550Y to be gain of function, we wanted to determine if the new variants exhibit a similar downstream impact on target protein expression levels when compared with S550Y and P342T. We also wanted to identify if all variants can be rescued with a known nRTK inhibitor. It is hypothesized that the new variants are gain of function and that all variants can be rescued with the inhibitor. Methods Using western blot analysis, the activation of ERK, JNK and nRTK was compared between wildtype (WT) and mutants. This in vitro method helped identify the degree of activation. For the second part of the study, HEK293T cells were treated with inhibitor to test for a rescue of phenotypes via western blot analysis. Results Results show an increased activation of nRTK, ERK and JNK in all variants with S550Y and S550F having the highest activation. Furthermore, pharmacological inhibition using small molecular kinase inhibitors resulted in decreased activation of nRTK, ERK and JNK suggesting a rescue of phenotypes. Conclusions Characterizing the downstream functional impact of these nRTK variants is an important first step to determine if gain of function nRTK mutations drive IBD. With a rising prevalence of IBD worldwide, these findings may lead to the development of pharmacological nRTK inhibitors as a novel personalized therapeutic approach for these patients and possibly for the broader IBD population. Funding Agencies CIHR

scholarly journals Identification of a β-Arrestin 2 Mutation Related to Autism by Whole-Exome Sequencing

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Yunfei Tang ◽  
Yamei Liu ◽  
Lei Tong ◽  
Shini Feng ◽  
Dongshu Du ◽  
...  
Keyword(s):  
Exome Sequencing ◽  
Whole Exome Sequencing ◽  
Developmental Stages ◽  
De Novo ◽  
Repetitive Behavior ◽  
Brain Regions ◽  
Autism Spectrum ◽  
Potential Contribution ◽  
De Novo Mutations ◽  
Whole Exome

Autism spectrum disorder (ASD) is a complex neurological disease characterized by impaired social communication and interaction skills, rigid behavior, decreased interest, and repetitive activities. The disease has a high degree of genetic heterogeneity, and the genetic cause of ASD in many autistic individuals is currently unclear. In this study, we report a patient with ASD whose clinical features included social interaction disorder, communication disorder, and repetitive behavior. We examined the patient’s genetic variation using whole-exome sequencing technology and found new de novo mutations. After analysis and evaluation, ARRB2 was identified as a candidate gene. To study the potential contribution of the ARRB2 gene to the human brain development and function, we first evaluated the expression profile of this gene in different brain regions and developmental stages. Then, we used weighted gene coexpression network analysis to analyze the associations between ARRB2 and ASD risk genes. Additionally, the spatial conformation and stability of the ARRB2 wild type and mutant proteins were examined by simulations. Then, we further established a mouse model of ASD. The results showed abnormal ARRB2 expression in the mouse ASD model. Our study showed that ARRB2 may be a risk gene for ASD, but the contribution of de novo ARRB2 mutations to ASD is unclear. This information will provide references for the etiology of ASD and aid in the mechanism-based drug development and treatment.

scholarly journals Functional characterization of BRCC3 mutations in acute myeloid leukemia with t(8;21)(q22;q22.1)

Leukemia ◽  
2019 ◽  
Vol 34 (2) ◽  
pp. 404-415 ◽  
Author(s):  
Tatjana Meyer ◽  
Nikolaus Jahn ◽  
Stefanie Lindner ◽  
Linda Röhner ◽  
Anna Dolnik ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Lines ◽  
De Novo ◽  
Functional Characterization ◽  
Interferon Response ◽  
Excellent Outcome ◽  
Recurrent Mutations ◽  
Primary Mouse ◽  
Inflammasome Activity

Abstract BRCA1/BRCA2-containing complex 3 (BRCC3) is a Lysine 63-specific deubiquitinating enzyme (DUB) involved in inflammasome activity, interferon signaling, and DNA damage repair. Recurrent mutations in BRCC3 have been reported in myelodysplastic syndromes (MDS) but not in de novo AML. In one of our recent studies, we found BRCC3 mutations selectively in 9/191 (4.7%) cases with t(8;21)(q22;q22.1) AML but not in 160 cases of inv(16)(p13.1q22) AML. Clinically, AML patients with BRCC3 mutations had an excellent outcome with an event-free survival of 100%. Inactivation of BRCC3 by CRISPR/Cas9 resulted in improved proliferation in t(8;21)(q22;q22.1) positive AML cell lines and together with expression of AML1-ETO induced unlimited self-renewal in mouse hematopoietic progenitor cells in vitro. Mutations in BRCC3 abrogated its deubiquitinating activity on IFNAR1 resulting in an impaired interferon response and led to diminished inflammasome activity. In addition, BRCC3 inactivation increased release of several cytokines including G-CSF which enhanced proliferation of AML cell lines with t(8;21)(q22;q22.1). Cell lines and primary mouse cells with inactivation of BRCC3 had a higher sensitivity to doxorubicin due to an impaired DNA damage response providing a possible explanation for the favorable outcome of BRCC3 mutated AML patients.

Recurrent De Novo Mutations of EPOR Gene in Primary Congenital Polycythemia.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1297-1297
Author(s):  
Mariluz P. Mojica-Henshaw ◽  
Caroline Laverdiere ◽  
Jaroslav F. Prchal ◽  
Josef T. Prchal
Keyword(s):  
De Novo ◽  
Stop Codon ◽  
Cell Mass ◽  
Hemoglobin Concentration ◽  
Erythropoietin Receptor ◽  
De Novo Mutations ◽  
Erythroid Progenitors ◽  
Increased Risk ◽  
Genetic Mosaicism

Abstract Primary familial and congenital polycythemia (PFCP) is a rare inherited disorder presenting with elevated red blood cell mass, elevated hemoglobin concentration and low levels of erythropoietin. Ten mutations in the erythropoietin receptor (EPOR) gene to date have been associated with PFCP. All of these mutations result in deletion of 59 to 82 amino acids from the carboxy terminal of EpoR which has been shown to contain a negative regulatory domain. Here, we describe a 2-year old boy of French-Canadian descent presenting with polycythemia and splenomegaly. Sequencing of the EPOR gene showed the proband to be heterozygous for a G to A transition in nucleotide 6002 (G6002A). The mutation generates a stop codon instead of tryptophan at amino acid 439, leading to a truncated EpoR. The association of the G6002A mutation in the EPOR gene with PFCP has been previously described in a large Finnish family (dela Chapelle et al., Proc Natl Acad Sci USA1993; 90: 4495) and in a 16-year old boy of English descent (Percy et al., Br J Hematol1998; 100:407). The G6002A mutation in both cases was considered to have arisen independently based on differences in a microsatellite polymorphism in the 5′UT of EPOR and the absence of the mutation in the immediate family of the English boy. We studied our proband’s parents for the G6002A EPOR mutation and did not find it. Their parentage was confirmed using 24 different microsatellite markers. This indicates that the G6002A mutation in the proband arose de novo. Since the mutation arose de novo, in vitro methycellulose cultures of erythroid progenitors isolated from peripheral blood of the proband were grown in the presence of increasing concentrations of Epo to rule out genetic mosaicism. The erythroid progenitors showed hypersensitivity to Epo as is characteristic of PFCP. However, we did not find evidence supportive of genetic mosaicism as all 70 BFU-E colonies analyzed were heterozygous for the G6002A mutation. Previously, two other polycythemia-associated EPOR mutations, 5974insG (Sokol et al., Blood1995; 86:15) and 5959G>T (Kralovics et al., Am J Hematol2001; 68:115) were shown to have arisen de novo. This case is thus the fourth instance out of 13 reported cases of polycythemia-associated EPOR mutations that has arisen de novo. Because of the rarity of polycythemia-associated EPOR mutations, their frequent de novo occurrence suggests that these mutations do not have a selective advantage but are detrimental. Their possible association with increased risk of thromboembolic and atherosclerotic disease due to chronically augmented Epo signaling is being explored by ongoing clinical studies.

scholarly journals SOX2 Plays a Critical Role in the Pituitary, Forebrain, and Eye during Human Embryonic Development

2008 ◽  
Vol 93 (5) ◽  
pp. 1865-1873 ◽  
Author(s):  
Daniel Kelberman ◽  
Sandra C. P. de Castro ◽  
Shuwen Huang ◽  
John A. Crolla ◽  
Rodger Palmer ◽  
...  
Keyword(s):  
Embryonic Development ◽  
Anterior Pituitary ◽  
De Novo ◽  
Hypogonadotropic Hypogonadism ◽  
Expression Patterns ◽  
Critical Role ◽  
Loss Of Function ◽  
De Novo Mutations ◽  
Direct Role

Abstract Context: Heterozygous, de novo mutations in the transcription factor SOX2 are associated with bilateral anophthalmia or severe microphthalmia and hypopituitarism. Variable additional abnormalities include defects of the corpus callosum and hippocampus. Objective: We have ascertained a further three patients with severe eye defects and pituitary abnormalities who were screened for mutations in SOX2. To provide further evidence of a direct role for SOX2 in hypothalamo-pituitary development, we have studied the expression of the gene in human embryonic tissues. Results: All three patients harbored heterozygous SOX2 mutations: a deletion encompassing the entire gene, an intragenic deletion (c.70_89del), and a novel nonsense mutation (p.Q61X) within the DNA binding domain that results in impaired transactivation. We also show that human SOX2 can inhibit β-catenin-driven reporter gene expression in vitro, whereas mutant SOX2 proteins are unable to repress efficiently this activity. Furthermore, we show that SOX2 is expressed throughout the human brain, including the developing hypothalamus, as well as Rathke’s pouch, the developing anterior pituitary, and the eye. Conclusions: Patients with SOX2 mutations often manifest the unusual phenotype of hypogonadotropic hypogonadism, with sparing of other pituitary hormones despite anterior pituitary hypoplasia. SOX2 expression patterns in human embryonic development support a direct involvement of the protein during development of tissues affected in these individuals. Given the critical role of Wnt-signaling in the development of most of these tissues, our data suggest that a failure to repress the Wnt-β-catenin pathway could be one of the underlying pathogenic mechanisms associated with loss-of-function mutations in SOX2.

scholarly journals Detection and phasing of single base de novo mutations in biopsies from human in vitro fertilized embryos by advanced whole-genome sequencing

2015 ◽  
Vol 25 (3) ◽  
pp. 426-434 ◽  
Author(s):  
Brock A. Peters ◽  
Bahram G. Kermani ◽  
Oleg Alferov ◽  
Misha R. Agarwal ◽  
Mark A. McElwain ◽  
...  
Keyword(s):  
Whole Genome Sequencing ◽  
Genome Sequencing ◽  
De Novo ◽  
Whole Genome ◽  
De Novo Mutations ◽  
Single Base

scholarly journals Variant-specific effects define the phenotypic spectrum of HNRNPH2-associated neurodevelopmental disorders in males

2021 ◽  
Author(s):  
Hans-Jürgen Kreienkamp ◽  
Matias Wagner ◽  
Heike Weigand ◽  
Allyn McConkie-Rossell ◽  
Marie McDonald ◽  
...  
Keyword(s):  
De Novo ◽  
Functional Characterization ◽  
Monozygotic Twins ◽  
Rna Recognition Motif ◽  
Neurodevelopmental Delay ◽  
Missense Variants ◽  
Mild Developmental Delay ◽  
Splicing Regulators ◽  
Pathogenic Variants

AbstractBain type of X-linked syndromic intellectual developmental disorder, caused by pathogenic missense variants in HRNRPH2, was initially described in six female individuals affected by moderate-to-severe neurodevelopmental delay. Although it was initially postulated that the condition would not be compatible with life in males, several affected male individuals harboring pathogenic variants in HNRNPH2 have since been documented. However, functional in-vitro analyses of identified variants have not been performed and, therefore, possible genotype–phenotype correlations remain elusive. Here, we present eight male individuals, including a pair of monozygotic twins, harboring pathogenic or likely pathogenic HNRNPH2 variants. Notably, we present the first individuals harboring nonsense or frameshift variants who, similarly to an individual harboring a de novo p.(Arg29Cys) variant within the first quasi-RNA-recognition motif (qRRM), displayed mild developmental delay, and developed mostly autistic features and/or psychiatric co-morbidities. Additionally, we present two individuals harboring a recurrent de novo p.(Arg114Trp), within the second qRRM, who had a severe neurodevelopmental delay with seizures. Functional characterization of the three most common HNRNPH2 missense variants revealed dysfunctional nucleocytoplasmic shuttling of proteins harboring the p.(Arg206Gln) and p.(Pro209Leu) variants, located within the nuclear localization signal, whereas proteins with p.(Arg114Trp) showed reduced interaction with members of the large assembly of splicing regulators (LASR). Moreover, RNA-sequencing of primary fibroblasts of the individual harboring the p.(Arg114Trp) revealed substantial alterations in the regulation of alternative splicing along with global transcriptome changes. Thus, we further expand the clinical and variant spectrum in HNRNPH2-associated disease in males and provide novel molecular insights suggesting the disorder to be a spliceopathy on the molecular level.

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